Aug 4 (Reuters) - Hopes of finding a treatment for the
deadly Ebola virus shifted on Monday to a small California-based
biotech company whose experimental drug has been used to treat
two American missionary workers.

The drug, developed by Mapp Biopharmaceutical Inc, was used
to treat two aid workers, one from the Samaritan's Purse group
and the other from Christian mission group SIM USA, who were
exposed to the disease in Liberia, according to a U.S.
government health official.

The Samaritan Purse aid worker, Dr Kent Brantly, returned to
the United States on Saturday for medical care, and his
colleague Nancy Writebol of SIM USA is due to fly back via
medical aircraft on Tuesday.

Samaritan's Purse said both the aid workers received the
experimental treatment while in Liberia.

News of the treatment, first reported by CNN, punctured a
share price rally in Canada's Tekmira Pharmaceuticals,
whose own experimental Ebola treatment had progressed to human
trials. The severity of the current outbreak in Africa, in which
nearly 900 people have died, has raised investor expectations
that Tekmira's treatment might move more quickly toward
regulatory approval.

The treatment developed by Mapp, called ZMapp, had only been
tested in monkeys. Treatment with experimental drugs that have
not gone through the customary series of clinical trials in
humans to determine safety and efficacy is highly unusual.

Privately-held Mapp and its affiliated commercial partner
Leaf Biopharmaceutical, said the biotech drug was only
identified as a potential treatment candidate in January and
that as a result very little ZMapp is currently available.
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